Rectal swabs useful for identifying enteropathogens in children

Last Updated: 2017-07-24

By Anne Harding

NEW YORK (Reuters Health) - Rectal swabs provide a higher overall yield than stool samples when used to detect pathogens in children with diarrhea or vomiting, according to new findings published in The Lancet Gastroenterology and Hepatology.

"When stool is not available, rectal swabs are an alternative that can provide important clinical information that would otherwise be unavailable," Dr. Stephen B. Freedman of the Alberta Children's Hospital and Research Institute at the University of Calgary, the study's first author, told Reuters Health in a telephone interview.

Analysis of diarrheal stool samples is the standard approach to detecting enteropathogens in children. But collecting stool specimens is unpleasant and difficult, and can lead to delays in diagnosis, Dr. Freedman and his team note in their report, published online July 13.

In the new study, Dr. Freedman and his colleagues compared stool testing and swab testing for identifying enteropathogens in 1,519 children who had at least three episodes of vomiting or diarrhea in the previous 24 hours, with symptoms lasting no longer than seven days.

Seventy-six percent of the participants provided stool specimens, while more than 99% provided swab specimens. The comparative yield adjusted odds ratios for stool versus swabs was 1.24 for children with diarrhea and 1.76 for children without diarrhea. But because stool samples were not collected for 24% of the study participants, the overall pathogen yield was higher with swab specimens (67% vs. 57%).

The percentage of stool specimens submitted "greatly exceeds submissions in previously reported studies," Dr. Freedman and his colleagues note, because the study funded a courier service for sample collection.

The Infectious Diseases Society of America and the American Society of Microbiology recommended against the use of rectal swabs for diagnosing enteropathogens in a 2013 report. However, Dr. Freedman noted, the technology involved in the swabs has improved in recent years, so they are more effective for collecting fecal material.

"It's really important that the knowledge about the diagnostic utility of rectal swabs be transmitted, communicated and worked into laboratory procedures," he said.

Dr. Eytan Wine of the University of Alberta in Edmonton, who wrote an editorial published with the report, told Reuters Health in an email, "In this study, Freedman and colleagues showed that rectal swabs provide an excellent alternative with a clear advantage of not requiring patients or parents to collect a sample at home and transport it to the lab; this can be taken in the doctor's office and sent for analysis immediately."

"Of note, in a 'real world' setting, stools samples are likely much more difficult to obtain," Dr. Wine added. "Guided by this study, I would suggest that when a physician determines that identifying the causative agent of the symptoms is required and stool is not provided/available in the office, collecting a rectal swab is an easy, cheap, and pain-free option that should be discussed with the patient/family."

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Lancet Gastroenterol Hepatol 2017.